下扬子及其邻区地壳和上地幔结构的接收函数研究及其地质意义
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本文为国家自然科学基金项目(41704092、41574092)和中国地质调查项目(编号12120114067701)联合资助成果。


A seismic receiver function study for the crustal and upper mantle structures of the Lower Yangtze and adjacent areas and its geological implications
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    摘要:

    本文通过对两条宽频地震密集台站剖面记录的远震事件进行接收函数分析,得到了切过下扬子地区的高分辨率地壳和上地幔顶部结构断面。接收函数结果揭示了此区主要块体结构特征以及地表出露晚中生代岩浆岩以及相关矿床下方的深部结构响应:①中生代以来新生或活化的地质构造对下扬子及其邻区地壳结构的控制作用明显;②在大别造山带中下地壳出现低速震相,指示了大别造山带下方地壳深部存在低速物质,可能是大别造山带下方地壳中发育的韧性剪切带,此韧性剪切带可能与大别超高压变质岩被抬升剥露于地表的动力学作用有关;③在江南造山带东段怀玉山地区中下地壳观测到褶皱和逆冲叠瓦状复杂转换震相结构,与江南造山带西段雪峰山地区中下地壳结构相似,可能反映了隐伏的元古代江南造山带;④在德兴矿床和皖南白垩纪花岗岩群正下方观测到Moho和LAB界面的突变上隆现象,可能指示了晚中生代以来在华南东部下扬子地区岩石圈的薄弱区域,软流圈的上涌造成了岩石圈地幔的局部破坏,壳幔结构的局部异常是壳幔物质相互作用的结果。以上地震学观测揭示了下扬子及其邻区下方一些重要的壳幔结构特征,反映了华南大陆东部在不同地质历史时期经历的独特构造演化事件,为我们深入理解华南板块的形成和早期演化以及后期中生代以来华南东部强烈的岩浆和成矿作用的深部机制提供了关键的地球物理约束信息。

    Abstract:

    We present here high- resolution seismic sections of crustal and uppermost mantle structures along two dense linear arrays across the Lower Yangtze region in a SE- NW orientation. Our seismic receiver function images reveal deep structural characteristics of the major blocks and deep structural responses of the late Mesozoic magmatic rocks and associated ore deposits. ①The crustal structures appear to be dominated by the newly initiated or reactivated geological features since the Mesozoic. ②Abundant low- velocity phases (indicating low- velocity materials) were observed in the mid- lower crust of the Dabie block. These low- velocity materials may act as the ductile shear zone in the deep crust, which is likely related to the dynamic processes responsible for the exhumation of the Dabie ultrahigh pressure metamorphic rocks.③We observed folded and imbricated seismic converters in the mid- lower crust of the Huaiyu Shan area in the eastern segment of the Jiangnan orogenic belt, which are analogous with previous seismic observation in the Xuefeng Shan area in the western segment and are interpreted as reflecting a buried Proterozoic Jiangnan orogen. ④The Moho and LAB discontinuities imaged exhibit local bulge deformation directly beneath the Dexing ore deposits and the Cretaceous South Anhui granite cluster, which probably indicate local mantle lithosphere destruction by asthenospheric upwelling in some weak zones of the lithosphere in the Lower Yangtze region during the Mesozoic. Our seismic observations reveal several significant subsurface features in the Lower Yangtze and adjacent areas that indicate distinct geological events during different evolving eras of the eastern South China continent. This provides critical geophysical constraints for understanding the formation and early evolution of the South China plate, as well as the deep mechanism of the intensive late Mesozoic magmatism and associated metallogenesis in eastern South China.

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叶卓,李秋生,张洪双,王晓冉,韩如冰,吴庆宇.2020.下扬子及其邻区地壳和上地幔结构的接收函数研究及其地质意义[J].地质学报,94(3):707-715.
YE Zhuo, LI Qiusheng, ZHANG Hongshuang, WANG Xiaoran, HAN Rubing, WU Qingyu.2020. A seismic receiver function study for the crustal and upper mantle structures of the Lower Yangtze and adjacent areas and its geological implications[J]. Acta Geologica Sinica,94(3):707-715.

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  • 收稿日期:2019-05-20
  • 最后修改日期:2019-08-28
  • 录用日期:2019-11-12
  • 在线发布日期: 2019-12-19
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